I think that people have been asking the wrong questions about wind
power. As Randall Parker notes,
wind is not a power source which can be turned up or down according to
the desires of the users; you either grab and make use of it when it's
blowing, or you do without.

People have been asking how much other grid generation could be
replaced by wind. The answer is "as things are now, not much of
the total", but I think this is the wrong question. A better
question is, "What uses can wind power serve, and what else might we
need to make it serve them?"

Uses of wind-electric power

Offhand, I can think of three major categories of uses for
intermittent, non-schedulable electric power sources like wind (which
are not mutually exclusive):

Produce power to allow other generation to be turned down, to
reduce fuel consumption and save wear and tear.

Produce energy for storage.

Produce energy for uses which currently do not use much
electricity, but can take advantage of the underutilized supply and idle
grid capacity.

Storing electricity is one of the most expensive things which can be
done with it. One strategy for storage is to convert the
electricity into the desired product and store that instead.
Consumers and electric utilities have used this system to good effect
for years: some consumers who use electric water heaters have them
on timers which switch them off during peak periods, and some larger
users of air conditioning purchase off-peak electricity at night to make
ice which is then used for cooling when electric costs are higher.

The applicability of these possibilities to wind power is
questionable. Across the cold north, winds blow strongest in the
winter rather than during the air-conditioning season and a great many
users heat water with gas rather than electricity. After motor
fuel, the greatest consumer of fuel in the average northern household is
space heat. What could wind power do to help with that?

This, of course, means Back Of The Envelope time....

What can you do with it?

Assuming the following:

The heating season is 180 days long;

The average household consumes 50 million BTU of natural gas per
year for space heat, of which 80% (40 million BTU) is captured and 20%
lost;

Another 7.5 million BTU is consumed during the heating season for
domestic hot water, also at 80% efficiency;

The available wind power per household is either 3 kW or 5 kW,
and the capacity factor of the wind turbines is 25%, 30% or 35%;

The efficiency of transmission and distribution is 90%, and there
are no grid-capacity limitations (cold weather and winter gales holding
little prospect for overheating of lines or transformers); and

The excess wind energy is used in resistance heaters to displace
natural gas, with 100% efficiency for space heat and 80% for water.

At the low end, the total wind energy delivered per heating season
is 2916 kWh (9.96 million BTU); at the high end, it is 6804 kWh (23.2
million BTU). Here's a grid of the per-household heat production
for various figures:

These figures are encouraging. Even a 21% reduction is quite a
bit compared to current gas needs; slashing requirements by 49% would be
phenomenal, and eliminate the prospect of gas shortages for some years
to come.

Someone's bound to ask if 5 kW of wind power is too much of a good
thing, supplying more energy during gales than could be used.
Well, maybe... but after you subtract 1 kW/household average for other
electricity, and recognize that the periods of highest wind are also the
periods of greatest heat loss through drafts, it doesn't look as if
overheating is a serious threat during the winter. The bulk of
that 49% savings would likely be realizable either in saved fuel at
generating plants or saved gas at homes and businesses.

Would we actually dump that much electricity as heat? Probably
not; it would make more sense to turn down other powerplants and use the
wind-generated electricity to run lights and motors (or charge cars)
before running it to resistance heat. But not all powerplants can
follow rapidly varying loads or compensate for fast ramps in other
capacity, like wind farms; this would require having enough generation
on-line to carry the system through the short-term lulls. If any
overage can be used to make space heat or hot water that we'd be using
anyway and avoid the need to burn fuel for that purpose, every bit of
wind power can be used productively even if it cannot be scheduled or
accurately predicted; the only abilities we need are to transmit it and
make the load follow the gusting wind.

The control systems required to perform such load management would
be useful for other purposes as well:

Extremely precise shedding of space heat loads in winter, and DHW
heating loads in any season;

Ability to maintain the entire electric-heating load as "spinning
reserve" (available for redirection as fast as control systems permit)
when excess generation requires it as a power dump, with positive
consequences for grid reliability.

What happens if you combine this wind-power system with widespread
home cogeneration systems and plug-in hybrids? I'm going to re-do
the scenario from cogeneration@home
using the 3 kW/25% and 5 kW/30% wind power figures from the above list,
and with DHW heat requirements added.

If the house requires the same 4320 kWh for its own consumption and
the car consumes 2520 kWh, total electric requirements are 6840 kWh for
the season or 38 kWh/day. The 3 kW wind system at 100% capacity
supplies 2.7 kW (64.8 kWh/day) or 26.8 kWh in excess of electric needs.
Further assuming that:

the wind supply is either at 100% or 0 (pessimal supply curve),

the entire 26.8 kWh (41%, 91,500 BTU/day) is surplus and must go
to heat,

all the heat can be used,

the DHW heat is supplied by a burner rather than the cogenerator,

DHW heat losses are unchanged, and

the new energy displaces fuel oil:

Fuel

Old
consumption

New
consumption

Δ consumption

Cost/unit

Δ cost

CO2 emission
per unit

Old emission

New emission

Δ emission

Wind
(3 kW, 25%
capacity)

0

2916 kWh

+2916 kWh

0

0

As electricity

0

1710 kWh

+1710 kWh

$0.05/kWh

+$85.50

0

0

As heat

0

41.2 mmBTU
(41.2 therms)

+41.2 therms

$0.02/kWh
(off peak)

+$24.12

0

0

Electricity,
coal-fired

4320 kWh

0

-4320 kWh

$0.08/kWh

-$345.60

3.4 lb/kWh

7.34 tons

0

-7.34 tons

Natural gas

575 therms

575 therms

0

$0.60/therm

0

11.52 lb/therm

3.31 tons

3.31 tons

0

Gasoline

288 gallons

0

-288 gallons

$2.00/gallon

-$576.00

19.4 lb/gallon

2.79 tons
e

0

-2.79 tons

Fuel oil

0

43.6 gallons

+43.6 gallons

$2.00/gallon

+$87.20

19.4 lb/gallon

0

0.42 tons

+0.42 tons

TOTAL

-$724.78

13.44 tons

3.73 tons

-9.71 tons

Fuel oil consumption in this case is reduced to less than 40% of the
original, and total petroleum consumption is cut by almost 80%.

What would happen if you could get 4.5 kW/household at 30% capacity
factor? On the days with wind the excess electricity creates
280,000 BTU/day of heat, or about 6% more than the average combined
space heat and DHW demand. It's likely that windy days are also
days of high heat demand, so I will assume that all of this heat can be
used and counted against total annual heating requirements.

Fuel

Old
consumption

New
consumption

Δ consumption

Cost/unit

Δ cost

CO2 emission
per unit

Old emission

New emission

Δ emission

Wind
(5 kW, 30%
capacity)

0

5832 kWh

+5832 kWh

0

0

0

0

As electricity

0

2052 kWh

+2052 kWh

$0.05/kWh

+$102.60

0

0

0

0

As heat

0

15.1 mmBTU
(151 therms)

+151 therms

$0.02/kWh
(off peak)

+$75.60

0

0

0

0

Electricity,
coal-fired

4320 kWh

150 kWh

-4170 kWh

$0.08/kWh

-$336.60

3.4 lb/kWh

7.34 tons

.26 tons

-7.09 tons

Natural gas

575 therms

505 therms

-70 therms

$0.60/therm

-$42.00

11.52 lb/therm

3.31 tons

2.91 tons

-.40 tons

Gasoline

288 gallons

0

-288 gallons

$2.00/gallon

-$576.00

19.4 lb/gallon

2.79 tons

0

-2.79 tons

TOTAL

-$776.40

13.45 tons

3.17 tons

-10.28 tons

In this case the remaining electric demand cannot be quite satisfied by
the cogenerator without discarding heat, so a small amount of
electricity is generated from coal again. Annual cost is down
slightly, carbon emissions are down more than 75% despite the
renewed reliance on coal, and petroleum consumption hits zero.
Gas consumption drops 12%. If the DHW supply was heated by
the cogenerator, coal use would be eliminated at the cost of somewhat
greater gas consumption.

Conclusions

Despite being unreliable and unschedulable, it appears that wind
could be used to offset fossil fuel consumption quite easily. In
the context of current systems it can be used to reduce fuel demand at
gas-turbine plants until they shut down; beyond this point it could be
used for space heat and domestic hot water, offsetting gas consumption
there as well. In a near-future system using cogeneration for all
space heat needs and grid-charged hybrid vehicles for transport, the
availability of wind could:

eliminate petroleum consumption during the heating season

reduce gas demand by 12%

reduce total carbon emissions by more than 75%.

Is it worth using? Looks like it to me.

UPDATE 5/23/05: Corrected typo in third table. Had to catch that one myself. So much for the eyeballs of the web as fact-checkers. ;-)
¶ 3/31/2005 10:15:00 PM

Comments:

Where did you get this: "The available wind power per household is either 3 kW or 5 kW, "?

Can you think of another way of stating what you meant where it might make more sense or be more precise? As it stands, it makes a shaky premise for an argument.

The figure for wind energy is a regulated fixed price. The two following come from rough spot prices in the Energy market. How can compete that expensive energy? The government, on grounds of environment protection, forces the electricity distributors to buy as much as it is available and the grid is able to handle without becoming unstable, thus, the EPCO's and partners that have built all those windfarms have their production subsidized. Is it fair?

In a free market, only a few locations would be able to produce competitive wind power, and even then, it would be a risky business.

Anonymous #1: Those are what are known as an "assumptions", which is why I ran through with two different ones. If you think they are unrealistic, try re-doing the calculations with something you like better.

Anonymous #2: Wind power in the USA is quite a bit cheaper. An AWEA page with a copyright date of 2000 lists figures from 6.56 cents/kWh down to 4.35 cents/kWh. The assumptions appear to be that both money and construction are cheaper in the USA, and the absence of huge subsidies means that the high-cost sites will not be used. This will keep the average down.

If you think the economics would be terribly different with non-surplus wind power going for a higher price, go ahead and post. I laid out my assumptions, and it should be simple to plug my numbers into any spreadsheet and then twiddle to your heart's content.